EP722850B1 discloses a low-permeability thermoplastic elastomer composition that is superior as a gas-barrier layer in pneumatic tires. This thermoplastic elastomer composition comprises a low-permeability thermoplastic matrix, such as polyamide or a blend of polyamides, in which there is dispersed a low-permeability rubber, such as brominated poly(isobutylene-co-paramethylstyrene), referred to hereinafter as BIMS. In EP857761A1 and EP969039A1, the viscosity ratio of the thermoplastic matrix and the dispersed rubber phase was specified both as a function of the volume fraction ratio and, independently, to be close to a value of one in order to produce a high concentration of small particle size vulcanized rubber particles dispersed in a thermoplastic phase. EP969039A1 further discloses that small particle size rubber dispersed in a thermoplastic resin matrix was important in order to achieve acceptable durability of the resulting composition, particularly where such compositions are intended to be used as innerliners in pneumatic tires.
Compositions exhibiting low gas permeability performance (i.e., functioning as a gas barrier) composed of thermoplastic resin/thermoplastic resin-based blends such as a high density polyethylene resin and nylon 6 or nylon 66 (HDPE/PA6.66), a polyethylene terephthalate and aromatic nylon (PET/MXD6), a polyethylene terephthalate and vinyl alcohol-ethylene copolymer (PET/EVOH), where one thermoplastic resin is layered over the other layer to form plural layers by molding, and processes for producing the same, are disclosed, for example, by I. Hata, Kobunshi (Polymers), 40 (4), 244 (1991). Further, an application regarding the use of such a composition as the innerliner layer of a tire is disclosed in Japanese Patent Application No. 7-55929. However, since these materials are thermoplastic resin/thermoplastic resin blends, while they are superior in gas barrier performance, they lack flexibility, and therefore, such films are liable to break when the tire is in use.
Thus, nylon polymers can be useful in polymer compositions for reducing the permeability of air and other fluids through a tire innerliner composition and elsewhere, for example, from the inside to the outside surface of a tire or hose. However, it is also known that nylon can be moisture sensitive or hygroscopic, the latter term being generally understood to mean that nylon will absorb moisture from the air. Consequently, moisture that may be present in the air contained in a pneumatic tire air chamber may be absorbed by the nylon present in a tire innerliner construction. The absorbed moisture may thereafter permeate through the various layers of a tire construction and, possibly, result in a bubble or blister within a layer or between layers thereby making it more susceptible to failure due to separation of the layers. In order to avoid such failures it is necessary to find a means of reducing the moisture vapor transmission rate of innerliner and other air or fluid permeation layers.
U.S. Pat. No. 5,738,158 discloses a pneumatic tire having an air permeation prevention layer or innerliner layer composed of a thin film of a resin composition including at least 20% by weight of a thermoplastic polyester elastomer comprised of a block copolymer of polybutylene terephthalate and polyoxyalkylene diimide diacid at a weight ratio of polybutylene terephthalate/polyoxyalkylene diimide diacid of 85/15 or less. The resin composition can further include dispersed rubber particles wherein the rubber particles have been dynamically vulcanized. The concept of using a resin composition as an innerliner layer has been further developed, see, e.g., U.S. Pat. No. 6,079,465, which describes a pneumatic tire that incorporates such an innerliner and discloses the use of various thermoplastic resins for use in the composition. This patent also discloses the presence of a tie layer and another layer to promote bond or adhesive strength of the innerliner layer in the overall structure. The further development of this technology to improve adhesion of the innerliner layer in the structure is described in U.S. Pat. No. 6,062,283 wherein melt viscosities and solubility parameters of thermoplastic resin components and elastomer components are controlled according to a specific mathematical formula. This patent also describes a pneumatic tire having an air permeation preventive layer comprising a low permeability thermoplastic elastomer composition comprising a thermoplastic elastomer having a thermoplastic resin composition as a continuous phase and a rubber composition as a dispersed phase, in which a barrier resin composition is contained, which low permeability thermoplastic elastomer composition has a phase structure in which the barrier resin composition is dispersed in the form of a flat state in the thermoplastic elastomer, is abundant in flexibility, is superior in gas permeation preventive property, and enables the tire to be reduced in weight. The patent also describes the use of a resin film layer to achieve coloration of the innermost and/or outermost surfaces of the tire.
U.S. Pat. No. 6,136,123 (and its divisional U.S. Pat. No. 6,402,867) describe a process for producing a pneumatic tire using, as an air permeation preventive layer, a strip-shaped or cylindrical-shaped single-layer or multiple-layer thermoplastic film, comprising: applying, to at least a part of the joining portion of the thermoplastic film or tire member facing the thermoplastic film, a tackifier-adhesive composition containing a polymer component having an absolute value of the difference of the critical surface tension with the rubber component of the tire member and the polymer component of the surface layer of the thermoplastic film of not more than 6 mN/m, respectively.
Other references of interest include: WO 2004/081107, WO 2004/081106, WO 2004/081108, WO 2004/081116, WO 2004/081099, U.S. Pat. Nos. 4,480,074; 4,873,288; 5,073,597; 5,157,081; 5,910,544; 6,079,465; 6,346,571; 6,538,066; and 6,814,118.